PERC study released on drainline carry of solid waste by low-flow toilets

I haven't dug through it yet. It's officially being released tomorrow (the 26th), but it looks like they've already posted it on the website. Hopefully this isn't a repost. I haven't seen anyone else post this, but I may have missed it.

Chicago, Ill. (November 26, 2012) â€” The Plumbing Efficiency Research Coalition (PERC) is pleased to announce that the long-anticipated study, The Drainline Transport of Solid Waste in Buildings, has been released and is now available on the PERC Website: http://www.plumbingefficiencyresearchcoalition.org. The study provides important insights into the performance of building drains and addresses opportunities for future research.

PERC was formed in January 2009 through a Memorandum of Understanding (MOU) to develop research projects that support the development of water efficiency and sustainable plumbing products, systems and practices. Projects are financed through government grants, foundations and private financing. The Coalition is comprised of industry organizations seeking to conduct much-needed research in a number of areas. PERC identified drainline transport as its first research project.

The six members of the coalition are represented by Mary Ann Dickinson, Alliance for Water Efficiency (AWE); Jim Kendzel, American Society of Plumbing Engineers (ASPE), Pete DeMarco, International Association of Plumbing and Mechanical Officials (IAPMO); Jay Peters, International Code Council (ICC); Gerry Kennedy, Plumbing-Heating-Cooling Contractors National Association (PHCC); and Barbara C. Higgens, Plumbing Manufacturers International (PMI).

â€œItâ€™s critically important that we gain a better understanding of how building drains perform as flows from plumbing fixtures, appliances and commercial equipment are reduced and toilet fixtures become increasingly stressed to singularly transport solid waste to sewers. This study identifies the controllable variables in the building drain system, such as slope, flush volume, toilet paper selection and toilet discharge attributes, and examines their relative significance on performance.â€ says DeMarco, who acted as the technical director for the study.

It looks like some of this will be no surprise to people who have read a lot on the topic or are knowledgeable in the area. Note, I'm not claiming I am knowledgeable.

Just a couple points I've picked out so far:

Toilet paper performance was a significant variable.

They had issues with 0.8 gpf performance. This is on page 47.

0.8 gpf / 3.0 Lpf flush volume: Observation of waste
movement within the Test Apparatus during the 0.8 gallon
(3.0 L) test runs clearly demonstrated a major difference in
performance when compared to the other volume levels
(1.28 gallons and 1.6 gallons). In five (5) of the sixteen (16)
test runs conducted at the 0.8 gpf / 3.0 Lpf volume, the test
media in the test apparatus compressed together to form
large plugs in the drain line that resulted in full-pipe or near
full-pipe conditions (see Photo 7-D). While these plugs
eventually cleared themselves prior to any water overflows
at the flush stand, the PERC TC still found that this flush
volume created a chaotic, unpredictable condition in 4-inch
pipe to the extent that the data at the 0.8 gpf / 3.0 Lpf
volume was mostly noise and not useable in the statistical
analysis.

Click to expand...

They found that 1.28 and 1.6 gpf was sufficient, if the drainline was in good condition. This is on page 48.

1.28 gpf/4.8 Lpf and 1.6 gpf/6.0 Lpf flush volumes- The
1.28 gallon (4.8 L) and 1.6 gallon (6.0 L) volumes resulted in
an orderly and predictable movement in the Test Apparatus
(see Photo 7-E and 7-F). In retrofit applications, it is
suggested that drainlines first be inspected for defects, root
intrusions, sagging or other physical conditions that could
result in clogging with lower flush volumes.